/Engine/Source/Editor/UnrealEd/Classes/MaterialGraph/MaterialGraphSchema.h
Allows schema to generate a tooltip (icon & message) when the specified asset(s) are dragged over the specified graph
virtual void GetAssetsGraphHoverMessage ( const [TArray](API\Runtime\Core\Containers\TArray)< [FAssetData](API\Runtime\CoreUObject\AssetRegistry\FAssetData) > & Assets, const [UEdGraph](API\Runtime\Engine\EdGraph\UEdGraph) * HoverGraph, [FString](API\Runtime\Core\Containers\FString) & OutTooltipText, bool & OutOkIcon ) const